1. Field of the Invention
This invention relates to a windproof umbrella which can be automatically restored to its normally closed condition after its cover is turned inside out by a strong wind from underneath, by simply operating a slider downwardly along a shaft as in the fashion of closing the normally-open umbrella into closed condition.
2. Description of the Related Art
Various windproof umbrellas of the aforesaid type have been proposed, for example, in UK Pat. GB 2110528b, U.S. Pat. No. 5,435,331 and U.S. Pat. No. 5,597,004.
Conventional umbrellas include a tension member which plays the leading function in restoring the umbrella from its turned over condition to a normally closed condition. Such tension members are composed of a steel wire having a diameter in the range from about 1.7 to 1.8 mm, with both ends being flattened out and punched with a hole for eyelet fixing. Alternatively, the wire may have a diameter of about 1.0 mm with both ends being formed into a loop also for eyelet fixing, and pivotally connected with the eyelet or rivet to a joint member and a stay, respectively.
In fabrication of these two types of the tension members, some problems have been experienced which hinder smooth function. Specifically, in the case of a steel wire of 1.7-1.8 mm diameter, the fabrication, i.e. flattening and punching of its ends, is difficult, hence a wire having a high hardness can not appropriately be used. To cope with these problems, a wire with a moderate hardness should be selected for the tension member. However, such tension member, when subject to a larger load, such as, for example, the tight cover or the weight of the wetted cover per se, is apt to bend or deform, as a consequence, lose its desired functions of pulling and pushing the joint member located at one side thereof when opening and closing the umbrella. Another shortcoming inherent in the use of high hardness steel wire is that it will generate a bigger shock against the cover when the umbrella cover is restored from the inverted position.
As regards the steel wire of a diameter of about 1.0 mm, which is conventionally and most preferably used in forming a tension member having at its both ends formed with a loop, it can not easily be formed into a true circle loop, leading to big tolerances which affect the pulling and pushing function of the tension member. In view of the foregoing problems inherent in the currently used tension member, provision of an improved tension member is being urgently contemplated.